Recap Science Café: How can the Dutch keep their feet dry?

Understanding the current state and future projections of sea level rise is crucial for developing effective protection or adaptation strategies. On June 1st, a Science Café – jointly organized by S4S and Water, Climate and Future Deltas – was held at the Vening Meinesz building, featuring three speakers who discussed the Netherlands' position and trajectory in relation to sea level rise. During this Science Café, we explored the details and predictions of sea level rise and how we may cope with or delay this.

Sea level rise: What, how, when?

During the first talk by Tim Hermans, an overview was presented of the current state and future perceptions of sea level rise. He shows that sea levels have been rising faster since 1900 than in the last 3000 years, and this rise is accelerating. This conclusion is supported by tide gauges and satellite altimetry. The impacts of sea level rise include increased chances of flooding, loss of ecosystems, and saltwater intrusions. The primary causes of global mean sea level rise are thermal expansion of the ocean, melting of glaciers and ice sheets, and groundwater extraction. However, it's important to note that global mean sea level rise does not uniformly affect all regions due to factors like vertical land motion and gravitational attraction of ice sheets. In fact, some areas may experience a fall in sea level. Projections of global mean sea level rise become increasingly uncertain as we look further into the future, emphasizing the need for accurate predictive models.

Sea levels are rising faster since 1900 than in the last 3000 years, and it is accelerating

Adapting to sea level rise

Building upon the first talk, Jaap Nienhuis discussed the available options for adapting to sea level rise. In the case of natural deltas, when sea level rise exceeds sedimentation rates, shorelines retreat. The Netherlands has historically responded to sea level rise by constructing dikes, following a protect-open approach to shield the delta interior. This strategy aims to maintain an open connection with the sea, allowing rising sea levels to extend upstream along rivers and flood harbor areas. This strategy requires significant dike improvements and brings the risk of salinization of surface waters. Alternatively, other adaptation strategies include a protect-closed approach (closing the sea completely off by dams, navigation locks, and sluices which requires large-scale water pumping), an advanced approach (extending the coastline seaward or creating a new coastline several kilometers offshore) or accommodation (‘living with the water’, allowing more frequent flooding). Many adaptation pathways across these approaches can be imagined. Adaptation pathways need to strike a balance between timely and sufficient measures, aiming to implement necessary actions while keeping options open for future adjustments.

Keeping dry feet by blocking the sun

Claudia Wieners explored in her talk the idea of actively combating sea level rise by artificial cooling. One intriguing approach she discusses is creating H2SO4 clouds, inspired by the Pinatubo eruption in 1991, to provide natural cooling and prevent thermal expansion. Additionally, strategies such as marine cloud brightening, cirrus thinning, sea ice preservation, and space-based solutions are explored. The implementation of these strategies is highly uncertain and raises political dilemmas. Nevertheless, Wieners emphasizes that exploring geoengineering strategies is essential to be able to make an informed decision.

Can we provide extra cooling agents to prevent thermal expansion?

By understanding the current state of sea level rise, considering adaptation options, and exploring innovative approaches, the Dutch can stay a step closer to keeping their feet dry and protecting their low-lying lands from the threats posed by rising sea levels. Nevertheless, uncertainties necessitate further research, and adaptation pathways require strong governance and policy decisions.